Shimon,
To filter records in the form's recordsource, you will want to use the
form's Filter and FilterOn properties. You would put the code to apply the
filters in the AfterUpdate event of your combo boxes. Here's a sample:
Dim strSQL as String
strSQL = "SELECT Field1, Field2, etc. FROM MyTable WHERE Field1 = " &
Me!cboCombo1 & " AND Field2 = " & cboCombo2
Me.Filter = strSQL
Me.FilterOn = True
Look up these properties in the online help. One note - you might also want
to but a command button on your form to turn off filtering to allow your
users to see all records.